Process for the pickling of metals



Patented Dec. I5, 1933 Fig PTEN

ERNEST CHAPMAN, F BLACKLEY, MANCHESTER, ENG-LAND, ASSIGNOR TO IMPERIAL GOAL INDUSTRIES LIMITED, OF LONDON, ENGLAND PROCESS FOR THE PICKLING- OF METALS No Drawing. Application filed January 8, 1929, Serial No. 331,161, and in Great Britain January 27, 1928.

oxide layer which is to be removed, but also the metal itself, and the result is a pitting of the metal surface, especially where scaling has exposed bare patches of metal, and also wastage of acid and metal. The object of my invention is to minimize or entirely avoid this attack of metal by the acid whilst facilitating, or at least not impeding, the solution of the oxide.

I have discovered that this object is achieved in a surprising manner by the addition to the acid bath of one or more compounds of the class of sulphonated hydrocarbon derivatives which possess the characteristic property of producing a precipitate in an acidified solution of glue or gelatine. As illustrative of the compounds within the general class as set forth above I mention the following compounds. The sulphonic acids of high boiling mineral oil fractions, which may or may not be condensed with aliphatic alcohols. When these sulphonic acids of high boiling mineral oil fractions are condensed with aliphatic alcohols there is produced an alkylated sulphonic derivative of the high boiling mineral oil fractions. These compounds may be prepared as disclosed in the applications Ser. Nos. 195,585 andv 205,833. filed by me and another, James Baddiley. Any of the sulphonic acids disclosed in these said copending applications may be used in my present process. Also sulphonated formaldehyde naphthalene or aldehyde-phenol condensation products may be used. Likewise alkyl naphthalene sulphonic acids and other polynuclear alkylated aromatic or hydroaromatic sulphonic acids may be used. These polynuclear alkylated sulphonic acids may be prepared by 1process claimed in the English patent speci cation No. 267,162 or the processes set forth in the said English patents as prior art methods. Any of the above-mentioned compounds the typical compounds or others of the same general class as set forth above may be employed. The compounds may be employed in the form of the free acids or in the form of a suitable salt which is soluble in the dilute acid employed in the pickling bath.

I find that'the addition of small amounts of any of these substances (up to 2 per cent of the weight of dilute acid, and in most cases very much less than 2 per cent) to the pickling bath effectively reduces and may even totally inhibit the attack of the metal by the acid, but does not hinder 'in any way the removal of the oxide from the metal surface.

From a large number of experiments I have made, the following may be quoted as illustrating the surprising results obtained:

1. A piece of steel was immersed in 25 per cent sulphuric acid at 19 0.; another exactly similar. piece of steel was immersed at 19 C. in 25 per cent sulphuric acid to which had been added 1 per cent of a sulphonated isopropylated mineral oil fraction (prepared as in the copending U. S.

application, Serial No. 195,585 by myself and Baddiley). In 385 minutes 45 cos. of hydrogen were evolved in the first case, and none at all in the second case.

The sulphonated isopropylated mineral oil fraction used above was prepared from a mineral oil fraction boiling between 150 and 300 C., by sulphonating the said fraction and condensing it with isopropyl alcohol. Mineral oil fractions boiling between 150 and 300 C. which have been extracted from petroleum with liquid sulphur dioxide are especially advantageous in producing these inhibitors, as mentioned in the acknowledged copending application, Serial No. 195,585.

2. Using 0.25 per cent of the sulphonated isopropylated mineral oil fraction instead of 1 per cent in the above experiment, 0.62 cos. of hydrogen was liberated in 271 minutes, compared With 42.1 ccs. in the same time in the absence of the inhibitor.

3. Using as inhibitor the sulphonic acid prepared according to the copending U. S. application, Serial No. 205,833, (by myself and Baddiley) 0.2 cc. compared with 47.7 ccs. of hydrogen was liberated in 215 minutes, This inhibitor was prepared (as described in the said application) from a min eral oil fraction boiling between 200 and 350 C. by adding somewhat more than one part of monohydrate of sulphuric acid to one part of said mineral oil fraction and heating the mixture to produce a complex sulphonated hydrocarbon derivative. The derivatives so produced are substantially dry solids, easily soluble in water both in the form of the free acid and as salts thereof. They possess marked wetting-out properties.

What I claim and desire to secure by Letters Patent is i 1. The improvement in the process for pickling of metals in acid media, which comprises treating the metal with the acid medium in the presence of alkylated sulphonic acids of high boiling mineral oil fractions.

2. The improvement in processes for pickling metal articles in acid media which comprises treating said articles with a liquid medium in the presence of an inhibitor, said liquid medium comprising a dilute mineral acid and a relatively small but effective amount of said inhibitor, said inhibitor being of the class of compounds which comprises complex sulphonated hydrocarbon derivatives which possess marked wetting out properties, said derivatives being obtainable from mineral oil fractions having a boiling point range between 200 and 350 C. and containing a relatively large amount of compounds capable of being sulphonated by mixing one part of said mineral oil fraction with more than one part of monohydrate of sulphuric acid, heating the mixture to produce a complex sulphonated hydrocarbon derivatiw and isolating the sulphonated material thus obtained, said complex sulphonated hydrocarbon derivatives being substantially dry solids easily soluble in water both in the form of the free acid'and as salts thereof.

3. The improvement in processes for pickling metal articles in acid media which comprises treating said articles with a liqu d medium in the presence of an inhibitor, said liquid medium comprising a dilute mineral acid and a relatively small but effective amount of said inhibitor, said inhibitor being of the class of compounds which comprises complex sulphonated hydrocarbon derivatives which possess marked Wetting out properties, said derivatives being obtainable from a sulphur dioxide extract of a mineral oil boiling between 260 C. and 300 C. and containing a relatively large amount of drate of sulphonic acid, heating the mixture to produce a complex sulphonated hydrocarbon derivative and isolating the sulphonated material thus obtained, said complex sulphonated hydrocarbon derivative being a substantially dry solid easily soluble in water.

4. The improvement in processes for pickling metal articles in acid media which comprises treating said articles with aliquid medium in the presence of an inhibitor, said liquid medium comprising a dilute mineral acid and a relatively small but eifectivc amount of said inhibitor being of the class of compounds which comprise complex sulphonated hydrocarbon derivatives which possess marked wetting out properties, said derivatives being sulphonated alcohol condensation products of a petroleum fraction extracted with sulphur dioxide and boiling between 150 C. and 300 0., possessing wetting out properties and soluble in water and acids.

In testimony whereof I aflix my signature.

ERNEST CHAPMAN.

compounds capable of being sulphonated, by

mixing one part of said mineral oil fraction with more than one part of monohy- 

